Bodde
Fractal Fanatic
EHX Bassballs
Ringmod - Dr. Scientist BitQuest is a GREAT one
Bitcrushing - Dr. Scientist BitQuest is actually great at this as well!
Good choices sir! Yes the Ringmod in the Axe fx can do nice things (especially octaver sounds) but it is not the best for the typical old school ring mod sounds like the Moogerfooger Ringmod does for example. The Bitcrush in the Axe fx is also nice for some things but also very limited.
But maybe what I miss the most is a really good electric Mistress (old one) flanger sound and a really authentic tape delay sound a la echoplex. I use my Catalinbread Belle Epoch for that now which is nicer (for me) than the tape delay algo in the Axe fx.
But instead of focusing on what the Axe fx can't do I concentrate on what it can do. Which is really much and that's why I love my Axe fx. You can't expect it to do it all because then you can get frustrated. If I miss something I buy the pedal and use it along with my Axe fx. I always take three extra pedals to gigs.